1. Field of the Invention
The present invention relates to a probe mark reading device and a probe mark reading method for reading probe marks formed on electrode pads by examining electrical characteristics of a prescribed object (for example, a semiconductor chip).
2. Description of the Related Art
Normally, in order to examine electrical characteristics of a semiconductor chip formed on a semiconductor wafer, pin-shaped test probes are pressed against electrode pads within the semiconductor chip. Electrode pads are typically made from aluminum and are typically covered in an insulating aluminum oxide covering formed by oxidation at the time of examination. The test probe is therefore pushed against the electrode pad with a certain amount of force in order to break through the covering. As a result, probe marks (contact imprints) are formed by the test probe. A determination can then be made as to whether or not the test probe has been correctly pushed against the electrode pad by reading probe mark conditions such as the presence or absence, position, and depth etc. of a probe mark.
In the related art, devices for observing conditions of probe marks using a microscope, devices that take photographs of the probe marks, and devices that take pictures of the probe marks using a CCD camera exist as probe mark reading devices for reading conditions for probe marks. In Japanese Patent Laid-open Publication No. Hei. 5-3230, a probe mark reading device is disclosed where a semiconductor wafer on which semiconductor chips are formed is mounted on a stage. Images obtained by taking pictures of probe marks formed on electrode pads with a CCD camera are then stored and displayed in an appropriate manner. With this configuration, age deterioration in a probe mark is checked and temporal changes in test probe pin-pressure and pin-shifts can be managed.
With devices detecting targets different from the electrode pads, such as, for example, tape inspecting devices for inspecting repetitive patterns disclosed in Japanese Patent Laid-open Publication No. Hei. 9-222311 (and the corresponding U.S. Pat. No. 5,808,744), mark position detection devices for detecting alignment marks on a wafer as disclosed in, for example, Japanese Patent Laid-open Publication No. Hei. 10-281729, or sample surface scanning devices for examining for foreign bodies or blemishes on a wafer surface disclosed in, for example, Japanese Patent. Laid-open Publication No. Hei. 10-281729, a target is sequentially photographed by moving the target and emitting a flash of light at the position of the target in a synchronized manner.
However, with the probe mark reading device of the related art disclosed in, for example, Japanese Patent Publication Laid-open No. Hei. 5-3230, it is necessary to carry out positioning by having a user move the semiconductor wafer mounted on a stage etc. so that probe marks formed on the electrode pads can be directly observed or photographed. However, in some cases there may be from a few tens of thousands to a few hundreds of thousands of probe marks on the wafer as a whole and reading the probe marks one at a time is both time-consuming and troublesome.
Moreover, devices for detecting a target different from an electrode pad, that move the target in the manner described above while taking a series of photographs also exist (for example, refer to Japanese Laid-open Publication No. Hei. 9-222311, Japanese Laid-open Patent Publication No. 10-281729, and Japanese Patent Publication No. Hei. 11-326233). According to these devices, photographing can take place in a short period of time without being troublesome to the user. However, with these devices, photographing is repeated at the same period and a photographing is carried out at a high-speed by making the picture-taking interval fixed. Therefore, as with electrode pads, the arrangement is unlikely to be at equal intervals, and it is not planned to take pictures at high speed of a target for which arrangement position may be changed (depending on the wafer). The above devices therefore cannot be easily used as devices for reading a multiplicity of probe marks formed at a multiplicity of electrode pads.
Further, in recent years, the number of times inspections are carried out is increasing with increases in the aspects of a chip that are tested electrically and with the complexity of test content. Cases where the position of a test probe is therefore shifted a little at a time to be parallel while tests are carried out to ensure that a hole is not made in an electrode pad of a thickness that is usually in the order of one micron are common. A plurality of probe marks are therefore formed on an electrode pad that has been subjected to a plurality of tests. It is therefore difficult to determine which of a plurality of probe marks is a probe mark formed by the final test. It is, however, possible to determine the position of the probe mark etc. from images photographed for the electrode pads by performing a difference operation in pixel units on an image for before the final test and an image for after the test. However, this kind of difference operation is extremely time consuming.